A variety of valves and various other devices are commonly fitted within a vehicle's fuel tank. It is common practice to connect such fuel accessories within a fuel tank by forming an aperture of a size comfortably accommodating the valve's housing, and fixedly attaching the valve by various means, e.g. welding, heat welding, different fasteners, etc.
However, this arrangement has several drawbacks. First, as a consequence of the above arrangement, a portion of the fuel accessories projects from an outside surface of the tank and further, and typically some tubing extends between the fuel accessories which also leis attached to the external surface of the tank.
Second, it is necessary to provide suitable sealing arrangements between the housing and the fuel accessory's housing which often has associated thereto some electric wiring or tubing.
It is thus a growing trend to form as little as possible openings in the tank (ideally only one), and accordingly venting system with its associated valves and connections are relocated as far as possible into the tank.
Another serious consideration concerned with vehicle fuel tanks is the ever-growing requirement of environment concerned organizations and authorities that the rate of fuel permeation from the fuel tank and its associated fuel accessories be minimal. The outcome of this requirement is that new connection means are now required for ensuring essentially permeation-free connection between the fuel accessories and the fuel tank.
Accordingly, it is becoming standard practice to manufacture multi-layered plastic fuel tanks having a substantive low permeation rate to fuel hydrocarbons, and where valves are fitted to such tanks with suitable sealing arrangements or heat welded to an inside wall surface of the tank.
Still another issue concerning connection of valves to vehicle fuel tanks is the effective operation level of the valves, namely the level at which the valve closes (at times referred to as cut-off or shut-off level) and the level at which the valve reopens. One of the considerations governing the operative level is space consuming which is of significant importance in particular in vehicles. It is thus a requirement that the “dead space” i.e. the space between “maximum fuel level” and the top wall of the fuel tank, be reduced to minimum, and care has to be taken not to increase the dead space.
Several patents are concerned with providing a fuel-impermeable attachment of the valve to the fuel tank. For example, U.S. Pat. Nos. 5,404,907, 6,035,883 and 6,289,915 disclose different weldable valve assemblies comprising a valve body extending through an opening formed in the fuel tank, and a weldable connector portion fastened to or integrated with the valve body, for welding onto the outer surface of the polymeric fuel tank.
Another method for attaching valves into a fuel tank is by thermo-forming two mating halves of the tank and pressing the valves and any other fuel accessories are pressed to the tank wall immediately after forming while still partially molten. Then, the two halves of the tank are attached and welded to one another. This method is time consuming and even more so there is a severe risk of leak or permeation through the line of weld of the two tank halves.
A different concept is disclosed in WO Patent Application WO0107806A1 also concerned with minimizing the dead space, wherein there is disclosed a fuel valve comprising a housing entirely received within a fluid tank wherein according to one application, the housing of the valve is formed at an uppermost portion thereof with a stem member for fixedly receiving within a corresponding receptacle formed at a top wall of the tank. According to a second application, the housing of the valve is formed at a top portion thereof with a first connecting member adapted for engagement with a corresponding second connecting member integral with a top wall of the tank, e.g. a snap-type connection.
Still another method for attaching fuel accessories to a fuel tank is disclosed in U.S. Patent Application Serial No. US20010013516A1 directed to the so called ‘ship in the bottle’ technique, where during blow molding of the tank one or more valves and other fuel accessories are supported by a support fitting (carrier member), whereby as the tank is formed it integrates with the support fitting by heat welding. This is a complicated and costly procedure.